Abstract: A device and method are provided to allow replacement of costlier motors with a retrofittable control board and a lower cost motors operating a several speeds to provide variable (but not continuously variable) blower airflow. The control signals normally used to command the motor being replaced are only used to detect the need to activate the blower motor; once detected, the control board activates the replacement blower motor by energizing a blower motor speed tap with the evaporator blower initially set to a high speed. Then the blower speed is lowered if a predetermined negligibly small, acceptable change in evaporator temperature has occurred. Given the number of speed taps on the replacement blower motor, the evaporator blower speed is continued to be reduced from the initially set high speed as long as there is only an acceptably small change in the measured evaporator temperature.

Abstract: A system and method are provided to allow the replacement of a costly electrically commutated blower or fan motor with a less efficient motor such as a permanent split capacitor motor operating at a predetermined speed, without regard to the specific electrically commutated motor command signals or programming being used by the original equipment manufacturer. A retrofittable control board is employed to activate the replacement motor by energizing the replacement blower motor when an electrically commutated blower motor command signal is observed on any one of the signal lines which are continuously monitored simultaneously.